${\mathrm{LaTiO}}_{3.5}$ is a layered compound made up of four ${\mathrm{LaTiO}}_3$ units: two regular perovskite units stacked between two distorted units that share an additional oxygen layer. In a single-crystalline thin film the (100) plane can be aligned parallel to the substrate surface, i.e., the additional oxygen layers are inserted parallel to the substrate surface. A detailed structural characterization reveals planar defects originating from substrate surface steps. These results, in combination with the in situ reflection high-energy electron-diffraction observations, suggest an oxidation mechanism using such antiphase boundaries as oxidation paths.

• Received 31 October 2000

DOI:https://doi.org/10.1103/PhysRevB.63.205401